The present trial was conducted to evaluate the supplementation effects of Macleaya cordata extract (MCE) on growth performance, serum biochemical parameters, and intestinal health of the juvenile American eel (Anguilla rostrata). The 480 juvenile American eels (10.93 ± 0.06 g) were randomly divided into four groups. They were fed on diets supplemented with MCE levels of 0, 25 mg/kg, 50 mg/kg, and 100 mg/kg for ten weeks, resp...